The Problem: Slight/mild sensorineural hearing impairment (HI) affects at least 180,000 US school-aged children. Although rapid advances have been made in the genetics of moderate-profound HI, little is known about the contributions of single gene mutations to slight/mild nonsyndromic Hl, or of the impacts of such HI on child outcomes. BROAD, LONG-TERM OBJECTIVES: This large-scale project, to be carried out in Victoria, Australia, will be the most comprehensive study yet to address the impacts and genetics of mild childhood hearing impairment. AIMS: In a large community sample of elementary school-aged children, we aim to (1) Describe relationships between slight/mild HI and Connexin 26 (the two most common "deafness genes") and Pendrin mutations, and impacts of slight/mild HI; (2) Develop and trial informed consent procedures on the use of DNA specimens for genetic testing for elementary school children with slight/mild HI; (3) Describe the impact of genetic testing on elementary school children with slight/mild HI and their families; and (4) Develop and evaluate education and counseling approaches when providing genetic information. RESEARCH DESIGN & METHODS: To establish prevalence, we will screen the hearing of approximately 6,000 elementary school-aged children (Years 1 and 5). From this base cohort approximately 180 children with slight/mild HI ("cases") and a further 360 children with normal hearing ("controls") will undergo assessment to address Aim 1. This will include testing the two "deafness genes" of interest, assessing language, academic, cognitive and social/quality of life outcomes, and self-reporting any problems with hearing. In a small preceding qualitative study, issues related to genetic testing in families of children with and without HI will be explored. We will then develop, trial and evaluate information and informed consent procedures, feedback, and counseling procedures (Aims 3 & 4). SIGNIFICANCE: If Cx26 and/or Pendrin is found to contribute to slight/mild HI, then this might profoundly alter (a) the advice and counseling we currently provide to families identified through a child with homozygous Cx26 or Pendrin deafness and (b) approaches to future population screening.